noun which may take the genitive case particle 'no'
suited to the occasion; expedient; ad hoc
Almost exclusively used in the set phrase 臨機応変 (りんきおうへん), meaning 'flexible, adapting to circumstances'. The standalone use is rare and literary.
「臨機応変」は、状況に応じて柔軟に対応することを意味する四字熟語です。
臨機応変 is a four-character idiom meaning to respond flexibly according to the situation.
この問題には臨機の処置が必要だ。
This problem requires an ad hoc measure.
From Chinese 臨機／临机 (línjī), meaning 'to face a situation'. In Japanese, it is almost always part of the compound 臨機応変.